X-ray anode current controller



Aug. 12, 1952 B; KALMON X--RY- ANODE CURRENT CONTROLLER Fied April 26, 195o -rll Patented Aug. 12, 1952 @607,011 .xf'nAnAnonn CURRENT, .CONTROLLER Kahnon, Cleveland,V Ohio Application Aceites, .1950, .serialfzNa .158,315

' e claims. (o1. 25o-97) ,'(fGrrantcdynnderf the act fof March 3,. S1883, .as

atube, therebytending tomaintainf'the anodefcursrent' =constant- HoWev-er', durinig-A operationfthe hiilaxnentof an X-.ray tube-changes .resistance due 'to Warming up, :with rfthe: vresult.itl'lat' the 'anode current-changes.

The-*apparatus :described vand claimed in the 12g-H1424, issued February "14', '193-9,1is .concerned Awith limiting thel currentto `provide `overloadpro tection 'and' employs 4equipmentquite edili-arent from that of applicants device.

The apparatus described vand olaimedwzinxthe patent to 4lvlutsc'heller for 'ilhermionic 'Cathode X-rf'ay Stabilizer iS-ystem, No. 15953389, :issued -itprilff 1934, -utilizesgrid control :of "thewanode 'current through vv`the medium of'fa'dditional "trio'de electron discharge tubes, fandfis.-conrplicatedtand 'The' apparatus embodying 'the finer/ant inven- `tion. overcomes 'the 'aforementioneddisadvantages tand limitations. :Vari-ations -anedecurrent :are -utilizedfto produce potentialdfferenoeswhich are amplified, `vand "appliedto "a inotor ior'pos'iti'oning the. arm ci va balancing :potentiometer `infseries 'with theprimary of thejlament transformer. and 'an Varrangement is provided 'forautomatically adjusting 'the 'filament current either 'to `increase or .decrease the same to maintain the anode, current .at apredetermned Value. Y

Accordingly, .it is `an obj ect .of the inveentionto ,provide new and improved .currentcontrolapparatus yfor ruse with .anelectron-discharge .tu-be.

Another Objectis to ,providenew `and.fin'ipi-'oy-.ed X-ray .anode currentcontrol apparatus.

`.Still another object tofprovide ne-wcand -.im proved anodecurrent controlfepparatus :in-which a balancing motorfcontrolledlirom lthefarrode cur- .amendelgprl .30, 1928; .370106,6. 75.7).

.2 l `ment potential vto maintain the anode-currentfat asubstantially constant value.

Other yobjects 'and advantages` willbecome apparent after a consideration of` the `:following specication taken in connection with the drawing in whic'hthe single'gure-thereof comprises va schematic electrical circuit diagram.

An X-ray tube ci" any convenient ldesign is shown, generally designated by 5 the reference numeral 23, and having anode 22 and filament '-24. The lament'is 'energized frornseconda-ry 25 cfa 'well insulatedv lament 'transformer having -a -primar-y- 29, vone fend of' which is lconnected byyerayfof lead" f3'l toone vside "of ia suitable A--CI supply source, 'not shown. The "other end' ofpr'mary 12B is connected by way ofthe-two -rheostats I30 and Vl3l, 4connected inseries'as' shown', f'to lead-'33 and :thence to the A.-"C. source. The larm`o`i'rheostat 3U is manually adjustable in a manner presently "to be described, While the larm ofrheosta'tf-3I is 'connected-by mechanical coupling '34 -to a reversi- `ble 'balancing motor` '33, which is designedfto run in two* directions selectively in accordance `.with the polarity of the potential applied thereto, and "which is-energizedffrom amplifier 3'2.

'Griefside of the aforementioned 'lament transformer) secondary -25 is connected to one terminal 'of-` the secondary Nora-high voltagetransformer lhaving primary -2-3, whichV is energized by -Way 'of lead-s 35 and 36 from the aferementioned fA.-'C. source, Vnot shown. lThe other terminal of' -secondary 21 is connected by way 'of mi1liamrne'ter26 "and capacitor A2| to Lanode 2-2. Anode 2l2-fis lfurther directly connected to ground l5, and `by way of the-series connected resistors 149 and -20Vto ymeter V2s. v

Ihejunction between vresistors 9 'and' 20 is connected to terminal 4| of a triple-polefdoublethrow switch 'generally designatedva't 50. Tervmin'al 42 o'f "the Aswitch 'is connected to 'one input terminalof the'ampliiie'r3'2, as shown. Ancde 22 -is connected Aby Wayo'f resistor |'3 *and lpotentiometer `|4 to *terminal 41 of the aforementioned switch i511. Connected in shunt -with the-afore- 'mentione'd elements I3 and" I-4 'is the series 'connectedbalttery il I vand current limitingresistor "I'2.

The junction :between resistor F13 and potentiome'ter M is connected 'to lswitchterminal#Brand thearm cri-potentiometer .t4 is connected'to :switch terminal M. Switch terminal L45 is A*connected to :the 'other "amplifier finput terminal;l fswitchf ter- .minal 46 is :connected tothe-blade 1H o'fanfad'ditional switch generally :designated im', w'lhichis operated vby .a fcam, rnotrshown, Vwntrcllezl ffrom Awhile the other terminal I 8 is connected to switch terminal 48.

The switch I0, which may be of conventional design, is normally closed on contact I8, and is so constructed and arranged that when the aforementioned/cam; not shown, and shaft or coupling 34 assume a predetermined position, the switch blade I'I makes simultaneous contact with both contacts I6 and I8.

The aforementioned amplifier 32 may be of conventional design, may have a balanced input to ground, and supply a potential of two polarities to motor 33 selectively in accordance with the polarity of the signal between the input leads to the ampliiier.

The operation of the aforedescribed apparatus is substantially as follows: When the triple-pole double-throw switch 50 is closed to the left in its Run position, the potential difference across resistor I9 resulting from anode current ilow is balanced against the potential drop caused by battery II in -resistor I3 and that portion of potentiometer I4 between the arm thereof and resistor I3. If these voltages are balanced, they will cancel in the input circuit to the amplifier, and motor 33 will not be energized.

Assume now by way of description that the anode current changes. The voltages are not longer balanced; motor 33 is energized and throughcoupling 34 adjusts the `arm of potentiometer 3| to reduce or increase the lament voltage and thereby restore the anode current to its former value. It will be understood, of course,` that the circuit is arranged so that an increase in anode current causes the motor to turn in a direction to move the arm of rheostat 3i to decrease the lfilament voltage, and vice versa. Y

In adjusting the equipment for correct operation, the following procedure may convenientlyr be followed: Switch 50 is closed to the right in Set position. The balancing motor then drives the compensating rheostat and cam until the armature of switch I is connected to both `coritacts. When this occurs, the input to the amplifier is effectively shorted, and the motor stops driving. Preferably this condition occurs when the arm of rheostat 3I is substantially in mid position. Rheostat 3D is then adjusted until the anode current has the desired or correct value as indicated on meter 26.

Switch 50 is then thrown to its Run position, and the arm of potentiometer I4 adjusted until the amplier is balanced, and the motor is unenergized. Thereafter the circuit will maintain the anode current substantially constant at the desired Value.v Y'

Whereas the invention has been described with reference to a particular embodiment thereof inwhich the anode current of an X-ray tube is regulated, itwill be understood that it is applicable to any electron discharge device where the current through any element thereof is proportionalv to the temperature of a filament or cathode. Filament 24 could, with equal facility, be the heater of a cathode type tube.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope Aof the appended claims the invention may be practiced otherwise than as specifically described.

l'l'his invention may be manufactured and-used ,b y or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. In apparatus of the character disclosed for regulating the current through an element of an electron discharge tubehaving an electron emitter wherein the emission is proportional to the creasing the temperature in accordance with the direction of rotation of the motor means thereby to control the yemission in accordance wit changes in said current. l

2. In apparatus of the' character disclosed for regulating the anode current of an X-ray tube having a iilarnent, in combination, means connected to said anode for obtaining a rst voltage proportional to said current, manually adjustable means for obtaining a second voltage, an amplifier, said first andl second voltages being applied in opposition to said amplifier, a reversible motor energized by the output of said ampliiier and 'rotating in two directions selectively in accordance with variations in the amplitude of said rst voltage above and below the amplitude of said second voltage, and a variable resistor controlled from said motor and connected to said filament for controlling the temperature and emission thereof in accordance with changes in said current.

3. In apparatus or" the character disclosed for regulating the anode current of an X-ray tube having a filament, in combination, resistor means'connected-in the anode-cathode circuit of said tube` for-obtaining a rst voltage proportional to said current, capaci-tor means connected in parallel with said resistor means, manually adjustable means including a potentiometer and a source of potential applied thereacross for obtaining a second voltage, an ampliiier, said first and second voltages being applied in opposition to said amplifier, a reversible motor energized by the output of said amplifier and rotating in two Adirections selectively in accordancewith variations in the amplitude of said rst voltage above and below the amplitude of said second voltage, and a-variable resistor having the resistance thereof controlled from said motor and connected to said filament for controlling the temperature and emission thereof in accordance with changes in said current.

4. In apparatus of the character disclosed for regulating the anode current of an X-ray, tube having a iilament, in combination, resistor means connected in the anode-cathode circuit of said tube for obtaining a rst voltage proportional to said current, a capacitor connected in shunt with saidresistor means, manually adjustable means including a potentiometer and a source of potential applied thereacross for obtaining a second voltage, switching means including a switch having first and second settings, an amplifier, means for applying said rst and second voltages in opposition'to said amplifier while the switch is in the first setting, a reversible motor energized by theoutput of said amplifier ljusts the variable resistor to a and rotating in two directions selectively in accordance with variations in the amplitude of said rst voltage above and below the amplitude of said second voltage, and a variable resistor having the resistance thereof controlled from said motor and connected to said filament for controlling the temperature and emission thereof in accordance with changes in said current, said switching means including means whereby while the switch is in the second setting the motor adpredetermined value.

5. In apparatus of the character disclosed for regulating the anode current of an X-ray tube having a lament, in combination: voltage divider resistor means connected in the anodecathode circuit of said tube for obtaining a iirst voltage proportional to said current, said anode being maintained at ground potential, said first voltage being a small fraction of the total anode voltage of said tube; capacitor means connected in shunt with said voltage divider resistor means; means for obtaining a second voltage of adjustable value, said last named means including a source of potential and first, second, and third resistors all connected in series in the order named, said second resistor comprising a po# tentiometer having a movable arm; the junction between said source and rst resistor being at ground potential; switching means including a switch having rst and second settings; an amplifier;y means for applying said first and second voltages in opposition to said amplier while the switch is in the first setting; a reversible motor energized by the output of said amplifier and rotating in two directions selectively in accordance with variations in the amplitude of said first voltage above and below the amplitude of said second Voltage; and a variable resistor having the resistance thereof controlled from said motor and connected to said filament for controlling the temperature and emission thereof in accordance with changes in said current; said switching means including means whereby while the switch is in the second setting the motor adjusts the variable resistor to a predetermined value.

6. In apparatus of the character disclosed for regulating the anode current of an X-ray tube having a lament, in combination: voltage divider resistor means comprising a pair of series connected resistors connected in the anode cathode circuit of said tube for obtaining a first voltage proportional to said current, said anode being maintained at ground potential, said first voltage being a small fraction of the total anode Y voltage of said tube; capacitor means connected in shunt with said voltage divider resistor; means for obtaining a second voltage of adjustable value, said last named means including a source of potential and first, second, and third resistors all connected in series in the order named, said second resistor comprising a potentiometer having a movable arm, the `junction between said source and said iirst resistor being connected to ground; a triple pole, double throw switch having first, second, and third contacts on one side thereof, iirst, second, and third arms, and fourth, fifth, and sixth contacts on the other side thereof opposite said first, second, and third contacts respectively; the junction between said pair of resistors being connected to said third contact; the junction between said first and second resistors being connected to said sixth contact; the arm of said potentiometer being connected to said second contact; an amplifier having a balanced input to ground; said secondand third arms being connected to the inputterminals of said amplifier; said iirst arm being connected to the junction between said second and third resistors; an additional switch having a fourth arm and having seventh and eighth contacts adapted to be closed or opened simultaneously; said seventh contact being connected to vsaid fourth contact; said eighthcontact beingconnected toiground; said fourth arm being connected to said fifth contact; said triple pole switch applying said rst and second voltages in opposition to said amplier while the triple pole switch is in a rst setting; a reversible motor energized by the output of said amplifier and rotating in two directions selectively in accordance with variations in the-amplitude of said first voltage above and below the amplitudeof said second voltage; and a variable resistor having the resistance thereof controlled from said motor and connected to said filament for controlling the temperature and emission thereof in accordance with changes in said current; said motor being also operatively connected to said fourth arm for moving the same, said triple pole switch when in the second setting energizing said amplier and motor to move said fourth arm to close the contacts associated therewith and short the input to said amplifier when the variable resistor assumes a predetermined value.

BEN KALMON.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 2,272,714 Lamb Feb. 10, 1942 2,492,304 Lundahl et al Dec. 27, 1949 2,496,717 Hansell Feb. 7, 1950 2,503,075 Smith Apr. 4, 1950 

